| Preserved, treated wood is commonly found in solid waste. Among the different types of preserved wood, chromated copper arsenate (CCA) treated wood recently has received much attention due to the scale of usage and its significant role in soil and water contamination. As the ash of CCA treated wood is hazardous, it cannot be burned, and the best available disposal method is thus landfilling. Leaching of the metals from disposed preserved wood in landfills pollutes the soil, water and the environment. The existing literature on leaching of CCA treated wood is reviewed, and several factors affecting leaching of the metals from wood, including pH of the leachant, temperature, the duration of leaching, the type of leachant are discussed. These factors affect each of the metals including chromium, copper and arsenic, differently. Definition and comparison of the effect of these mentioned factors on each preservative metal several experiments were performed. In all experiments ground wood (remaining at the top of sieve No. 10) was soaked in leachant (ratio 1:10). The leachants were nitric acid, sulfuric acid and acetic acid (0.1N), having pH values of 3, 4 and 5. They were left in an incubator for 5,10 and 15 days. The temperature of the incubator was set to 15°C for 15 days and then the experiment was repeated for temperatures 25°C and 35°C. On the other hand to investigate the biodegradability of the leached wood, unleached wood and some of the leached wood samples were chosen. The necessary nutrients for growth of fungi and soil were added and the amount of generated CO2 was measured through the experiment. The results of the experiments showed that sulfuric acid (pH3) is the most effective leachant. Most of the leaching happens in the first 5 days and temperature increases the amount of leached metals. The leached CCA wood is still resistant to biodegradation. |
